1. Field of the Invention
This invention generally relates to intracardiac instruments and methods, and more particularly to an intracardiac catheter and a method with the capability for electrical sensing, pressure sensing and cardiac pacing that is especially well suited for detecting, diagnosing, and treating myocardial ischemia.
2. Description of Related Art
Present applicant has previously demonstrated the efficacy of utilizing a specially designed intracardiac catheter for detecting ischemia induced experimentally by partial coronary artery stenosis in dogs. (See the paper entitled "Intracardiac Electrode Detection of Early or Subendocardial Ischemia" by S. Siegel, et. al, Pace, Vol. 5, December 1982, pages 892-902. Also, the abstracts entitled "Detection of Ischemia with an Intracavitary Electrode" by S. Siegel, et. al, Pace, Vol. 5, March-April 1982, page 307; "Intracardiac Electrode Detection of Early or Subendocardial Ischemia" by S. Siegel et. al, Circulation Vol. 66 Part II, page 367; Onset of Ventricular Fibrillation" by S. Siegel et. al, Pace, Vol. 6, page A-136; and "Detection of Ischemia Presaging Ventricular Arrhythmias in Canines" by R. Brodman, S. Siegel et. al, Chest, Vol. 86, page 324.) The catheter disclosed in the above references included an elongated body having a lumen form therein. Electrical conducting means was contained within the lumen extending from a monitor at the proximal end to an electrical activity sensing electrode at the distal end.
The distal end of the catheter was placed in the ventricle of the heart. Analysis of resulting electrocardiographs demonstrated a correlation between the stenoses produced and the sensed electrogram.
Although potentially useful for detecting ischemia, the intracardiac catheter utilized in those references may have detected a variety of superimposed variables. The proximity of the sensing electrode to the ischemic area may have been variable and was not evaluated. Cardiac function may change drastically within seconds based upon any number of variable factors which are interrelated such as changes in volume status, peripheral vascular resistance, heart rate, rhythm and cardiac output. Cardiac output may significantly affect myocardial function and secondarily result in changes in myocardial perfusion or ischemia.
Proper diagnosis of ischemia as a primary event (e.g. spasm, graft closure, coronary thrombosis causing ischemia) or secondary event (e.g. due to hypovolumia; hypertension; tachycardia; bradycardia; pulmonary edema; loss of atrial kick; drop in cardiac output; etc.) is critical to accurate diagnosis and formulation of an appropriate plan of treatment. Thus, the previously disclosed catheter, although useful in detecting myocardial ischemia, lacked the capacity to diagnose and treat the problem.